Generator brush tool



May 17, 1949. R. K. CLARK GENERATOR BRUSH, TOOL Filed April 10, 1946Patented May 17, 1949 GENERATOR BRUSH TOOL Robert K. Clark, UnitedStates Army, St. Paul, Minn.

Application April 10, 1946, Serial No. 661,046

1 Claim.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370O. G. 757) The invention described herein may be manufactured and usedby or for the Government for government purposes without the payment ofany royalty thereon.

The present invention concerns the proper inspection of generators andthe like, particularly such as exciters or battery charging generatorsof small internal combustion power plants.

In direct current generators the brushes ride on a commutator, inclosedby a ported case closed by a removable band covering ports over thebrushes. They require occasional replacement for various reasons wellknown. Brushes are not easy to remove because of the lack of space toinsert ones hand. A brush is held in place and caused to ride in closecontact with the commutator surface by a spring which although capableof exerting a substantial force is easily sprung (permanently deformed)if pushed roughly aside. When the brush spring is sprung it is no longercapable of holding the brush in firm contact with the commutator. Theresultant arcing under the brush accelerates wear and erosion of thebrush and commutator, with impairment of generator efficiency and dangerof shorting the armature windings and burning out of the gen erator. Theinvention offers a tool which enables clearing the brush spring from thepath of removal of the brush with a minimum liability of damage to thespring.

Because of the diflicult it is not uncommon for generator inspectors tomerely remove the cover band and attempt to inspect the commutator andthe brushes without removing the latter. It is here sought to facilitatemoving of the brush spring to clear the brush, and to enable removal ofthe brush with greater ease, so that liability of careless inspectionwill be counteracted.

It is an object of the invention to provide a simple tool which willgrasp the brush spring and permit easy removal of the brush.

Referring to the drawing:

Fig. 1 is a side elevation of the tool, stretched, in lifting engagementwith a brush spring, the latter indicated in dotted lines.

Fig. 2 is a front view of the tool, with a brush assembly and part of agenerator case dotted in, the tool being dotted in its liftingengagement with the brush spring and in deflected position of thehandle.

Fig. 3 is a view similar to Fig. 1 with the tool in a free state.

The tool comprises a pencil-shaped handle portion II] which may be ofWood or metal in a size suitable for insertion in a pencil pocket of aworkmans garment, although its size may vary depending on the size ofthe generator installation with which it is used. The lower end may betapered as at H. The larger upper end portion of a helical wire springI2 is fitted over and around the end II and fastened to handle portionl0 by screw or other fastening means, so that the adjacent intermediateportion of the spring tends to be held coaxial with the handle.

Spring I2 is in the form of a conical helix normally close coiled, abouttwo and a half inches long, more or less and is made of wire of abouttwenty-six S. W. G. In normal or free condition coils of the springtouch each other.

The tool is provided with a spring-engaging head I3 preferably of steelor other metal, having a shank portion I i fitting into and connectedcoaxially to the free end of spring l2. It will be noted that there is acentral portion i5 of spring l2 between handle Ill and shank portion itwhich is free to flex or bend. Head 16 is provided with substantiallyparallel bifurcations iii of about three-sixteenths of an inch or morein length extending outwardly from shank portion i i substantiallyperpendicular to the axis of handle portion or rod l0, so that the headis generally L-shaped. The space ll between bifurcations it is such asto receive at least one turn of the coil of a generator brush spring.

Shank portion I4 is likewise fastened to spring l2 as described above byuse of screws or equivalent means. Spring I2 may be tapered throughoutits length from rod Hi to shank portion M if desired. In small jobs itmay be replaced by a flexible strip of metal.

In use the band customarily fitted around the generator case, andcovering openings in the case over the generator brushes, is removed,and the tool is inserted in the opening. The head it is manipulated sothat bifurcations l5 grasp extend across (one over and one under) a coilof the generator brush spring which thus becomes engaged in space I1. Inthis condition, the major part of the spring I2 extends outwardlythrough the adjacent port of the case and beyond the latter, and thehandle is movable by flexing of the spring l2 as may be required toeffect the placement of the head l3. Handle It? is then raisedsymmetrically stressing the generator brush spring until clear of thebrush, after which the brush may be readily removed. In this use of thetool the spring l2 may be bent to avoid obstruction of the handle bygenerator case parts or other parts, and after sufficient displacementof the end of the brush spring the handle may be pressed to one sidewhile the brush spring remains confined by the head l3, so as to clearthe case port and afiord free access to the and commutator. Afterremoval and inspec o the brush is replaced or renewed and the springreadjusted on the brush and released from the tool.

It will be noted that the generator brush spring is compressedsymmetrically, not pushed to one side and distorted so as to acquire apermanent ofi center set or be unable to firmly press the brush intocontact with the commutator.

What I claim is:

A tool for lifting the brush spring of a dynamo electric machine of thegeneral character described, comprising a handle body having a taperedhelical spring extended therefrom, said spring having a normallyrectilinear axis, but being extensible and flexible under stress of ahandle laterally of a generator case opening while.

a brush spring is supported by the tool, said spring having abrush-spring-engaging head at its extremity comprising a substantiallyL-shaped rigid body having its shank portion secured coaxially to theextremity of said spring, two parallel closely spaced lateral arms beingformed at the outer extremity of the head and spaced from each other ina plane coincident with the axis of said shank to receive a convolutionof a spring therebetween.

ROBERT K. CLARK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,758,504 English May 13, 1930Wiessner Jan. 5, 193 7

